1. Field of the Invention
The present invention relates generally to RF components, and particularly to RF splitters/combiners.
2. Technical Background
It is often desirable to divide an incident RF signal into two or more versions of the incident RF signal. The input RF signal is often split into two (2) output signals by a single 1×2 splitter. The RF signal may be split into more than two output signals (e.g., 4, 8, 16, 32, etc.) by cascading stages to form a splitter network. One important objective of the splitter is to divide the RF signal equally into the various output signals with minimum insertion loss. Insertion loss refers to the dissipation of signal power within the splitter itself. Insertion losses may be the result of signal power being converted into thermal energy (i.e., I2R losses) or from other causes. There are various types of splitters that may be employed to form a splitter network. Unfortunately, each of the various types has drawbacks associated with them.
In one approach that has been considered, Wilkinson type hybrid power dividers are employed to create a multi-stage network. This approach has several drawbacks including narrow bandwidth characteristics. While the inventor of the present invention has found that a network of this type often has superior performance at relatively high frequencies, it will perform poorly at lower frequencies. Furthermore, this approach is also impractical at lower frequencies because of size considerations.
Resistive power splitter networks have also been considered. These types of networks, theoretically at least, have infinite bandwidth, but the insertion loss is too high (3 dB above 3 dB splitting loss) to be of practical use. Another drawback relates to the fact that the isolation is limited to 6 dB.
In yet another approach, the use of wide-band balun technology based on the Guanella style balun has been considered. However, Guanella style baluns do not have adequate bandwidth. Another drawback to this approach relates to the lack of isolation between the output ports. This feature could cause significant ripple in the response due to various mismatches in the network.
In yet another approach, a lumped element splitter network has been considered. This approach works well at relatively low frequencies; however, the insertion loss and return loss performance degrades rapidly above a relatively low frequency.
What is needed is a splitter/combiner system that is configured to split an incident RF signal into many output signals over an ultra-wide signal bandwidth without substantial insertion losses.